I agree that as a FT mother it is nice to have a break from time to time in order to do things that are difficult with a baby in tow. If you have no family nearby or even in the same country, it can be hard to ever get a break during the day.

Spend the time with your child perhaps and pay someone £10 an hour to tidy your house? Since you have a nanny for 2 mornings a week you already have loads of time off to do things for yourself. I have no nanny and no nursery, we spend a tenner a week on a cleaner and get the rest of the jobs done in the evening when the baby is asleep (my partner does his fair share as he realises that I spend the daytime taking care of the baby)

Leaving aside all the comments about 'high end', I think that you may need to revise your thinking about childcare costs/arrangements in central London.

£10 per hour, net (so £10 plus tax, NI and ERNIC on top) is the standard rate for a nanny.

Babysitters might be a bit less.

A childminder would also be cheaper.

Some nurseries do register to do 'emergency' or 'ad hoc' are through sites such as 'emergency childcare', but this varies from nursery to nursery. The cost for this at the nursery I use is a whopping £16 per hour....

There is an 'exclusive' family members' club - including gym, toddler groups and creche in Parsons Green which might be worth taking a look at. I know it's not Notting Hill, but sounds like what you are after. Non members can use the crèche for up to 2 hours and they also have drop off toddler groups where staff will supervise your child at tumble tots / messy play type stuff.